The present invention relates to a method for purifying a fluoroaryl metal compound such as bis(pentafluorophenyl)dimethyltin or bis(pentafluorophenyl)dibutyltin, which is useful, for example, as a pharmaceutical and agricultural chemical intermediate, a polymerization catalyst, a polymerization co-catalyst, a catalyst for photopolymerization of silicone, and intermediates of these catalysts.
A fluoroaryl metal compound such as bis(pentafluorophenyl)dimethyltin or bis(pentafluorophenyl)dibutyltin is a useful compound, for example, as a pharmaceutical and agricultural chemical intermediate, a polymerization catalyst, a polymerization co-catalyst, a catalyst for photopolymerization of silicone, and intermediates of these catalysts.
For example, J. Chem. Soc., (1964) 4782 discloses a method for reacting pentafluorophenyl magnesium bromide, obtained by reacting bromopentafluorobenzene with magnesium by means of the Grignard reaction using diethyl ether as a solvent, with dimethyltin dibromide over two days at a reflux temperature, and for synthesizing bis(pentafluorophenyl)dimethyltin in a yield of 58 percent. In the foregoing production method, since diethyl ether, which is a compound having a low boiling point, is used as the solvent, it is difficult to control the temperature of a reaction system, and special caution is required in handling diethyl ether as it is highly flammable.
Besides, for example, Organometallics., (1998) 5492 discloses a method for reacting pentafluorophenyllithium, obtained by reacting bromopentafluorobenzene with butyllithium at xe2x88x9278xc2x0 C. using diethyl ether as a solvent, with dimethyltin dichloride at xe2x88x9278 C., and for synthesizing bis(pentafluorophenyl)dimethyltin in a yield of 95 percent. However, in the foregoing production method, it is required to cool down a reaction system to xe2x88x9278xc2x0 C., which is difficult to carry out industrially.
In the production method described in J. Chem. Soc., (1964) 4782, the reaction of pentafluorophenyl magnesium bromide and dimethyltin dibromide produces not only the bis(pentafluorophenyl)dimethyltin, which is an object, but also magnesium dibromide, which is magnesium halide, as a by-product. Since magnesium dibromide is soluble in a solvent such as diethyl ether, in order to purify the bis(pentafluorophenyl)dimethyltin, it is necessary to remove the magnesium dibromide from a solution.
For example, J. Chem. Soc., (1964) 4782 and WO 00/17208 (published on Mar. 30, 2000) disclose a method for removing magnesium halide by treating a reaction solution containing the magnesium halide with an aqueous ammonium chloride solution.
However, when the reaction solution is treated with the aqueous ammonium chloride solution, it becomes difficult to separate an organic layer and an aqueous layer. Therefore, it is hard to say that purifying the bis(pentafluorophenyl)dimethyltin obtained, for example, by the production method described in J. Chem. Soc., (1964) 4782, by means of, for example, the purifying method described in J. Chem. Soc., (1964) 4782 and WO 00/17208 is industrially advantageous. Incidentally, when a fluoroaryl metal compound containing magnesium halide as an impurity is used, for example, as a polymerization catalyst, the activity of the catalyst is significantly decreased.
Consequently, a method for easily and inexpensively purifying a fluoroaryl metal compound produced by various producing methods has been desired.
It is therefore an object of the present invention to provide a method for purifying a fluoroaryl metal compound easily and inexpensively, so as to obtain a highly pure fluoroaryl metal compound having no impurities.
In order to attain the foregoing object, a method for purifying a fluoroaryl metal compound of the present invention, which is represented by General Formula (1): 
where each of R1, R2, R3, R4, and R5 independently represents one of a hydrogen atom, a fluorine atom, a hydrocarbon group, and an alkoxy group, provided that at least one of R1-R5 represents a fluorine atom, M represents a metal atom which belongs to the group IV, R6 represents a hydrocarbon group, and n represents one of 1 through 3,
is characterized by including the step of precipitating and removing magnesium halide represented by General Formula (2):
MgXaXb xe2x80x83xe2x80x83(2) 
where Xa represents one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and Xb represents one of a chlorine atom, a bromine atom, and an iodine atom,
from a solution containing the fluoroaryl metal compound, the magnesium halide, and an ether solvent.
In other words, to attain the foregoing object, the method for purifying a fluoroaryl metal compound of the present invention, which is represented by General Formula (1), is characterized by including the step of removing magnesium halide, which is represented by General Formula (2), from a solution containing the fluoroaryl metal compound, the magnesium halide, and an ether solvent, by treating the solution with an acid.
Further objects, features, and advantages of the present invention will be fully understood by the following description. Also, benefits of the present invention will be apparent from the following explanation.